[en] The specific purpose of this work is to provide a better understanding of the ¹⁴C level structure: the general purpose is to provide the details for using shell model calculations in R-matrix analyses. Using the TOF facilities of the Ohio University Accelerator Laboratory, the elastic and first 3 inelastic differential scattering cross sections for ¹³C + n were measured at 69 energies for 4.5 ≤ E_n ≤ 11 MeV. A multiple scattering code was developed which provided a simulation of the experimental scattering process allowing accurate corrections to the small inelastic data. The integrated ¹³C(n,α)¹⁰Be cross section is estimated. The sequential 2n-decay of ¹⁴C states populated by ¹³C + n was observed. A shell model code was developed. Normal and non-normal parity calculations were made for the lithium isotopes using a new two-body interaction. The results for ⁵Li predict the 2s_1/2 and 1d_5/2 single-particle states to be located below the 3/2⁺ (E_x = 16.66 MeV) state. Similar calculations were made for ¹³C, ¹³N, and ¹⁴C. Shell model calculations generated the R-matrix parameters for the elastic and first 3 inelastic channels of ¹³C + n. After adjusting some energies, the predicted structure generally agrees with experiment for E_n < 4 MeV. The procedure for using shell model calculations in R-matrix analyses is given. New and more consistent ¹⁴C level information is obtained

[en] The specific purpose of this work is to provide a better understanding of the ¹⁴C level structure; the general purpose is to provide the details for using shell model calculations in R-matrix analyses. Using the TOF facilities of the Ohio University Accelerator Laboratory, the elastic and first 3 inelastic differential scattering cross sections for ¹³C + n were measured at 69 energies for 4.5 ≤ E/sub n/ ≤ 11 MeV. A multiple scattering code was developed which provided a simulation of the experimental scattering process allowing accurate corrections to the small inelastic data. The integrated ¹³C(n,α)¹⁰Be cross section is estimated. The sequential 2n-decay of ¹⁴C states populated by ¹³C + n was observed. A shell model code was developed. Normal and nonnormal parity calculations were made for the lithium isotopes using a new two-body interaction. The results for ⁵Li predict the 2s/sub 1/2/ and 1d/sub 5/2/ single-particle states to be located below the 3/2⁺ state. Similar calculations were made for ¹³C, ¹³N, and ¹⁴C. Results for ¹³C and ¹³N show for E/sub x/ < 10 MeV the Thomas-Ehrman shifts are related to the 2s/sub 1/2/ single-particle energies. For ⁷Li and ¹⁴C, 2 h-barω calculations were done. Shell model calculations generated the R-matrix parameters for the elastic and first 3 inelastic channels of ¹³C + n. After adjusting some energies, the predicted structure generally agrees with experiment for E/sub n/ < 4 MeV. Previous elastic ¹³C + n data were refit to replace R₀ background terms by more realistic broad states and to get better agreement with model calculations. R-matrix fitting of the full data set produced new ¹⁴C level information. For E/sub n/ > 4 MeV (E/sub x/ > 12 MeV), 5 states are given definite J/sup π/ assignments; 3, tentative assignments. 122 refs., 91 figs., 30 tabs

[en] With the availability and maturity of several evaluated nuclear data files, it is timely to compare the results of integral tests with calculations using these different files. We discuss here our progress in making integral benchmark tests of the following nuclear data files: ENDL-94, ENDF/B-V and -VI, JENDL-3, JEF-2, and BROND-2. The methods used to process these evaluated libraries in a consistent way into applications files for use in Monte Carlo calculations is presented. Using these libraries, we are calculating and comparing to experiment k_eff for 68 fast critical assemblies of ^233,235U and ²³⁹Pu with reflectors of various material and thickness

[en] A Hamiltonian employing a ''physical'' central two-body potential has been used for simultaneous calculation of both normal and non-normal parity states of p-shell nuclei. Normal parity states have been calculated in a full 0/h bar/ω space and non-normal parity states in a full 1/h bar/ω space with the effects of spurious center-of-mass states completely removed. No explicit core is used in any of the shell model calculations. Results are compared with experimental data and previous shell model calculations for the following nuclei: ⁴He, /sup 5,6,7,8/Li, ⁸Be, /sup 13,14/C, and ¹³N. 34 refs., 9 figs., 3 tabs

[en] The shell model/R-matrix technique of calculating nuclear reaction cross sections for light projectiles incident on light nuclei is discussed, particularly in the application of the technique to thermonuclear reactions. Details are presented on the computational methods for the shell model which display how easily the calculations can be performed. Results of the shell model/R-matrix technique are discussed as are some of the problems encountered in picking an appropriate nucleon-nucleon interaction for the large model spaces which must be used for current problems. The status of our work on developing an effective nucleon-nucleon interaction for use in large-basis shell model calculations is presented. This new interaction is based on a combination of global constraints and microscopic nuclear data. 23 refs., 6 figs., 2 tabs

[en] LLNL's interactive system for nuclear data evaluation uses a general-purpose two-dimensional graphics code, QPX. With simple commands, the authors access and plot any information in the Livermore evaluated neutron data library (ENDL), activation library (ACTL), or charged-particle library (ECPL), the Livermore experimental cross section information library (ECSIL), or any evaluated data library using the ENDF format. Features of this system important to evaluation work are discussed. The conversion of evaluations from the ENDF format to the ENDL format for use in this system is discussed

[en] Shell Model calculations have been carried out using a full spsdpf 2hω, model space and a PMM interaction. The neutron and alpha particle channels have been calculated and compared to our recently completed experiments for various methods of managing the strong interaction between the 0hω and 2hω states. Preliminary results with Warburton and Browns interaction will also be reported

[en] This report contains short papers on nuclear data measurements, calculations, and evaluations

[en] New evaluations of the total reaction cross sections for ²H(d,n)³He, ²H(d,p)³H, ³H(t,2n)⁴He,³H(d,n)⁴He, and ³He(d,p)⁴He have been completed. These evaluations are based on all known published data from 1946 to 1990 and include over 1150 measured data points from 67 references. The purpose of this work is to provide a consistent and well-documented set of cross sections for use in calculations relating to fusion energy research. A new thermonuclear data file, TDF, and a library of FORTRAN subprograms to read the file have been developed. Calculated from the new evaluations, the TDF file contains information on the Maxwellian-averaged reaction rates as a function of reaction and plasma temperature and the Maxwellian-averaged average energy of the interacting particles and reaction products. Routines are included that provide thermally-broadened spectral information for the secondary reaction products. 67 refs., 18 figs

[en] This document provides a discussion of charged-particle evaluations for applications; advanced modeling of reaction cross sections for light nuclei; thermonuclear data file (TDF) -- a processed file for thermonuclear applications; evaluation of (n,2n) reactions on isotopes of Y and Zr; extension of the LLNL evaluated nuclear database (ENDL) to 30 MeV; and calculated kerma values